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Overview
Comment:Add system requirements for ductile behavior.
Timelines: family | ancestors | descendants | both | trunk
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SHA1: e56e9ebd70109cc210e00b6e89ad4596b2e94617
User & Date: drh 2008-08-07 16:31:55
Context
2008-08-08
15:46
Continuing work on syntax requirements. This is just an incremental check-in. check-in: b45c611781 user: drh tags: trunk
2008-08-07
16:31
Add system requirements for ductile behavior. check-in: e56e9ebd70 user: drh tags: trunk
11:33
Merge changes back into a single branch. check-in: 420b6c5ef7 user: drh tags: trunk
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Changes to pages/sysreq.in.

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<tcl>
sysreq S10000 {} {
  SQLite is an SQL database engine.  And the fundamental task of
  every SQL database engine it to translate the abstract SQL statements
  readily understood by humans into sequences of I/O operations readily
  understood by computer hardware.  This requirement expresses the
  essesence of SQLite.
} {
  The SQLite library shall translate high-level SQL statements into
  low-level I/O calls to persistent storage.
}

sysreq S10100 S10000 {
  SQL is one of the worlds most widely known programming languages,
................................................................................
  attack.
} {
  The SQLite library shall support prepared statement objects with
  late parameter binding
}

</tcl>












































<h2>8.0 Summary Of System Requirements</h2>

<p>The foregoing contained both system requirements and explanatory
text interspersed.  The following is a reproduction of the system
requirements without the explanatory text, as a convenient reference.
The top-level system requirements are shown first, followed by lower-level
system requirements that provide additional detail.</p>

<h3>8.1 Top-level System Requirements</h3>

<tcl>
foreach {id derivedfrom text} $sysreq_list {
  if {[llength $derivedfrom]>0} continue
  hd_puts "<blockquote><b>$id:</b>"
  hd_resolve $text
  hd_puts </blockquote>
}
</tcl>

<h3>8.2 Derived System Requirements</h3>

<tcl>
foreach {id derivedfrom text} $sysreq_list {
  if {[llength $derivedfrom]==0} continue
  hd_puts "<blockquote><b>$id:</b>"
  hd_resolve $text
  hd_puts </blockquote>
}
</tcl>







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<tcl>
sysreq S10000 {} {
  SQLite is an SQL database engine.  And the fundamental task of
  every SQL database engine it to translate the abstract SQL statements
  readily understood by humans into sequences of I/O operations readily
  understood by computer hardware.  This requirement expresses the
  essense of SQLite.
} {
  The SQLite library shall translate high-level SQL statements into
  low-level I/O calls to persistent storage.
}

sysreq S10100 S10000 {
  SQL is one of the worlds most widely known programming languages,
................................................................................
  attack.
} {
  The SQLite library shall support prepared statement objects with
  late parameter binding
}

</tcl>
<h2>8.0 Ductile Failure</h2>

<tcl>
sysreq S80000 {} {
  A common characteristic of digital systems (as opposed to analog
  systems) is that digital systems tend to be brittle.  In other words,
  digital systems tend to work perfectly with no sign of stress until 
  they fail utterly and completely.  The behavior is like a
  physical object that holds its shape as external
  loads increase, until it shatters without warning.</p>
  
  <p>In most circumstances, ductile failure is preferred over brittle
  failure.  A ductile device begins showing signs of
  trouble well in advance of failure.  Physical objects bend and/or crack,
  providing operators with warnings of overload and an opportunity
  to take corrective action, while continuing to function for as long
  as possible.</p>
  
  <p>Digital systems have a reputation for being brittle, yet brittleness
  is not an intrinsic property of digital systems.  Digital systems can
  be designed to continuing functioning outside their design parameters
  while providing operators with warning of possible trouble.  But there
  most be focused effort on the part of the designers to make digital
  systems ductile.  With analog systems, the ductileness tends to be
  inherent in the medium, but with digital systems ductileness needs
  to be explicitly added.
} {
  SQLite shall exhibit ductile failure characteristics
}

sysreq S80100 {S80000} {
  SQLite strives to deal gracefully with anomalous behavior by
  the application or by its own internal subsystems.  Yet graceful
  handling of out-of-band inputs is of no value if the anomaly goes
  unreported.  The problems must be visible to the
  application so that warnings and alarms can be propagated to operators.
  The useful aspect of ductile failure is that it gives advance warning.
  Ductile behavior is of no use to anyone if nobody can see the part
  bending.
} {
  SQLite shall make anomalies visible to the application
}

</tcl>
<h2>9.0 Summary Of System Requirements</h2>

<p>The foregoing contained both system requirements and explanatory
text interspersed.  The following is a reproduction of the system
requirements without the explanatory text, as a convenient reference.
The top-level system requirements are shown first, followed by lower-level
system requirements that provide additional detail.</p>

<h3>9.1 Top-level System Requirements</h3>

<tcl>
foreach {id derivedfrom text} $sysreq_list {
  if {[llength $derivedfrom]>0} continue
  hd_puts "<blockquote><b>$id:</b>"
  hd_resolve $text
  hd_puts </blockquote>
}
</tcl>

<h3>9.2 Derived System Requirements</h3>

<tcl>
foreach {id derivedfrom text} $sysreq_list {
  if {[llength $derivedfrom]==0} continue
  hd_puts "<blockquote><b>$id:</b>"
  hd_resolve $text
  hd_puts </blockquote>
}
</tcl>